Muller's method applies to both real and complex functions, but here we
restrict ourselves to real functions.
This class differs from MullerSolver in the way it avoids complex
operations.

Muller's original method would have function evaluation at complex point.
Since our f(x) is real, we have to find ways to avoid that. Bracketing
condition is one way to go: by requiring bracketing in every iteration,
the newly computed approximation is guaranteed to be real.

Normally Muller's method converges quadratically in the vicinity of a
zero, however it may be very slow in regions far away from zeros. For
example, f(x) = exp(x) - 1, min = -50, max = 100. In such case we use
bisection as a safety backup if it performs very poorly.